Researchers at IBM's Almaden, California research lab are building
what will be the world's largest data array--a monstrous repository of
200,000 individual hard drives all interlaced. All together, it has a
storage capacity of 120 petabytes, or 120 million gigabytes.

There are plenty of challenges inherent in building this kind of
groundbreaking array, which, says, IBM, is destined to be used for, as Technology Review writes, "an unnamed client that needs a new supercomputer for detailed
simulations of real-world phenomena." For one thing, IBM had to rely on
water-cooling units rather than traditional fans, as this many hard
drives creates heat that can't be subdued in the normal manner. There's also a
sophisticated backup system that senses the number of hard disk failures
and adjusts the speed of rebuilding data accordingly--the more
failures, the faster it rebuilds. According to IBM, that should allow it
to operate with the absolute minimum of data loss, even none.

IBM's also using a new filesystem, designed in-house, that writes
individual files to multiple disks so different parts of the file can be
read and written to at the same time.